The medical speciality of diagnostic radiology has long had the ability to observe abnormalities using x-rays or x-ray fluoroscopy. These abnormalities can often be biopsied or localized in preparation of surgery because both the abnormality and the metallic needle can be seen under x-rays.
The nature of nuclear medicine imaging techniques allows the abnormality to be seen, but non-radioactive materials or objects such as a conventional biopsy needles cannot be seen. To allow pre-surgical localization or biopsy using nuclear medicine techniques, a radioactive needle must be used.
In U.S. Pat. No. 4,781,198 issued to Kanabrocki, a biopsy needle for this purpose is described. This needle is coated with a radioactive metal and then subsequently coated with another layer of stable metal. The problem with this approach is that for use in the human body, the outer layer must be as chemically non-reactive as possible. Some of the metals that can be plated are highly toxic or irritating to the skin. To be useful in humans, the outer layer must therefore be composed of a biologically and chemically inert material such as gold. If the needle is to be stored for any length of time prior to use, the outer layer must also prevent any chemical oxidation from occurring and must be able to tolerate sterilization procedures.
A standard stainless steel needle cannot be plated with gold without prior surface preparation, as gold is not readily adherent to stainless steel. The needle as described by Kanabrocki is functional, but lacks the means by which an outer layer of gold can be plated onto it.